Device Length Dependency of Cross Gain Modulation and Cross Phase Modulation in Semiconductor Optical Amplifier

The cross gain modulation, the cross phase modulation and their recovery time in the SOAs with the various lengths were experimentally investigated. It was found that these values strongly depended on the device length.     

Simulation of Fast-Recovery Cross-Modulation Characteristics in Semiconductor Optical Amplifier with Assist Light

We analyzed the characteristics of cross-modulations (XM) and their recovery times in a semiconductor optical amplifier by a newly-developed TMM. The calculated results suggest faster recovery of the XMs by introducing a high-power assist light.     

Preparation and properties of silica films with higher-alkyl groups

Silica films with various types of alkyl groups were grown from the liquid phase, at room temperature, using alkyl tri-alkoxy silane compounds. From Fourier transform infrared (FTIR) absorption measurements, a majority of Si-alkyl bonds in the source molecules were found to remain in the grown film, while Si-alkoxy bonds were completely removed. Electrical and thermal properties have been measured comparatively for various films having dense alkyl groups. The films with the methyl group are promising for silicon production in ultra large-scale integrated circuits (Si-ULSIs) and the film having the vinyl group for non-heat-tolerant compound-semiconductor large-scale integrated circuits (LSIs).     

Optical nonlinearities in semiconductor optical amplifier and electro-absorption modulator: their applications to all-optical regeneration

Semiconductors have large optical nonlinearity with response speed in the several tens of picosecond range, making them ideal use as all-optical regenerators and wavelength converters. We theoretically and experimentally investigated optical nonlinearities induced by carrier dynamics both in forward biased semiconductor waveguide (SOA) and in reverse biased semiconductor waveguide (EAM). We made a detailed theoretical study of carrier dynamics in semiconductor waveguides by using the newly developed time-dependent transfer matrix method. To confirm the simulation results, we propose utilizing a polarization discriminating delayed interferometer (PD-DI) configuration as a simple technique for measuring optical nonlinearities such as cross gain modulation (XGM), cross absorption modulation (XAM), and cross phase modulation (XPM). In the first part of the paper, we reviewed SOA-based regenerators. As expected from the simulation results, we confirmed that injection of the transparent assist light was very effective in reducing of the SOA gain recovery time of down to a few tens of picoseconds. We further demonstrated 40 Gbit/s regeneration using an SOA-one-arm MZI (so-called UNI) configuration. The superior regeneration capability of two-stage UNI was successfully confirmed by a recirculating loop experiment up to 30,000 km with 150 regenerations. In the latter part of the paper, we reviewed all-optical regenerators using EAM. A bit-synchronized rf-driven XAM 3R regenerator consisting of only one EAM for both gating and timing correction was demonstrated at 20 Gbit/s. An EAM in conjunction with delayed interferometer configuration, which utilizes XPM as well as XAM in the EAM, has structurral simplicity and fast regeneration operability up to 100 Gbit/s. The fast response of EAM allows the optical regeneration with a small pattern word effect.     

Growth mechanism of Si-faceted dendrites

The growth mechanism of Si-faceted dendrite was studied using an in situ observational technique. We directly observed the growth processes of Si-faceted dendrites from Si melts. It is found that triangular corners with an angle of 60 degrees are formed at the dendrite tip. We present an original growth model for faceted dendrites based on the experimental evidence. The model fully explains the growth process of faceted dendrites.     

Examination of the reactivity of hydroxy groups in multioxygenated cyclohexanoids: synthetic study toward cytotoxic pericosine B

The reactivity of two hydroxy groups in some multioxygenated cyclohexanoids was examined for basic study of the synthesis of the cytotoxic marine natural product pericosine B and related compounds. Differences in reactivity for O-methylation or O-acylation among substrates were observed.     

Polarography in polymer science

A review of polarography in polymer science is presented.     

Behavior of the fast cyclotron wave in a nonuniform magnetic field

The fast cyclotron wave becomes unstable and is excited in a spiral electron beam-plasma system when the perpendicular energy component of the beam is sufficiently large. When a nonuniform magnetic field is applied to the system, the cyclotron frequency as well as the parallel velocity component of the beam vary spatially. It is confirmed experimentally, that the variation affects the excited wave and results in a spatial variation of its wavenumber in the way predicted by the dispersion relation of the fast cyclotron wave.